There are many examples of battery operated radio frequency (RF) devices, such as RF Short Range Devices (SRD), RF Automatic Meter Reading (AMR) devices, active RFID devices and battery assisted passive RFID devices. A problem associated with RF devices which include an RF section and a power source, is that the battery impedance and/or battery metallic parts may affect the RF section of the device. This is especially so when the device includes a larger battery. As such, it is desirable to isolate the effect of the battery impedance and/or the battery metallic parts from the RF section of the device in order to improve the performance of balanced RF components such as: amplifiers, modulators, demodulators and antennas.
Methods used to RF isolate a battery from an RF section include physical separation of the battery whereby the battery is physically remote from the RF section. An additional solution is design of the antenna to prevent the problem. However, in certain battery operated radio frequency devices, wherein the antenna cannot be easily redesigned or wherein the device is thin and flexible, these methods may not be effective.
The following patents and publications were cited in a parent case, the disclosures of all of which are incorporated herein by reference: U.S. Pat. Nos. 4,703,327, 6,097,347 and 5,778,306, US patent publication numbers US 2005/092845 and US 2005/275591, PCT publication numbers WO 2006/031580 and WO 00/640004, EPO publication number EP 1,450,240 and GB patent publication GB 2,326,799.
RFID devices that include a battery utilize an ASIC for the RF components and such ASIC is putatively designed to not be affected by the battery, even if not additionally isolated therefrom. See for example, the EM4324 data sheet from December 2008 (after date of invention of instant application), showing that direct connection of an antenna and battery to an ASIC is a proper manner.